Transit accommodation in Doha
 

I just booked OSL - DOH - HKG - DOH - HKG with CX (Qatar operates the OSL - DOH legs) in business, on the way home, i arrive at DOH 22:00, and my flight to OSL doesn't leave until 07:45 the next day.

Since CX and QR have a partnership on this route, will i get a hotel room i DOH for the night, like QR does with their passengers on 8+hrs layovers?

But your entire ticket is on QR document , with QR flight numbers right? Then you have to check with QR and not CX. Even if you are with CX flight number, CX will only provide STPC in HKG when you arrive and depart on a CX flight number.

Since at DOH, you are neither arriving and departing with a CX flight number, there is no STPC with CX.

No.
It's booked with CX on CX flight numbers. Only exception is DOH - OSL which is on QR flight number (kinda strange since OSL - DOH has a CX flight number).

I assumed I wouldn't get a hotel. But the flights were so cheap (QR wanted 1300usd more for the same flights for example), so i can afford a hotel in Doha for the night, or even just hang in the lounge with some movies.

That's why its 'cheap'. Contact CX reservation and asks them if you qualify for STPC anyway?